1. Field of the Invention
This invention relates to compositions for removing coatings from surfaces.
2. Discussion of the Prior Art
Compositions for removing paints, varnishes, and other coatings have been available for many years. Most of these compositions fall within two general classes. The first type attacks the coating by the chemical action of the ingredients thereof, which generally comprise alkalis or acids. This type of coating remover comprises alkali and acid compositions, such as those described in U.S. Pat. Nos. 3,681,250; 3,615,825; and 3,972,839. The alkali or acid compositions require considerable post-removal treatment to insure complete removal of the alkali or acid, and have been found to discolor wood. The second type depends upon the solvent power of the constituents of the composition to dissolve or at least soften the coatings. In the second type, it is customary to use aromatic hydrocarbons, lower aliphatic esters, ketones, alcohols, chlorinated solvents, or similar organic solvents. However, the vapor pressure of such liquids is high, with the result that they evaporate quickly, thereby rendering it difficult to adhere to a surface for a sufficiently long time to remove coatings therefrom. It has been proposed to overcome this difficulty by gelling the solvent, for example, by adding a wax thereto. Although these solvents have received wide usage and have been found to have acceptable coating removal qualities, their use is being questioned on the grounds of the safety hazards they present to the users thereof, namely toxicity. Moreover, many of the solvents having a high vapor pressure present a fire hazard, on account of their low flash points and ignition temperatures U.S. Pat. No. 4,120,810 discloses the use of N-methyl 2-pyrrolidone and a mixture of aromatic hydrocarbons having more than six carbon atoms as a paint stripper effective on a wide range of surfaces and capable of penetrating many layers of paint per application primarily because of its slow evaporation rate. This material suffers from the high cost of raw materials and the suspected toxic effects of the aromatic materials used.